Austempering is a commercially important heat treatment operation, where strong and tough bainitic steel is produced in a single heat treatment. During the austempering process, the steel is first austenitized and then cooled rapidly to just above the martensite start temperature until bainite nucleates and grows, usually until the transformation stops and then it is cooled to room temperature. Due to the sluggish solid state transformation kinetics, industrial austempering necessitates isothermal holds of 2 to 24 hrs, depending on the size and composition of steel. The conventional austempering process is carried out at a constant (isothermal) temperature. The duration of the austempering process as well as the resultant microstructure depends on the holding temperature and component size.